Question for those using ballast puppy pumps

I am trying to put the final touches on my ballast system design. I am going to be running two ballast puppy pumps off of one 1 1/4" floor intake. Here are my questions...

1. Is there any problem just reversing the pumps and emptying the sacs right back out through the floor intake?

2. Or do I need to somehow empty the water out a side thru-hull?

3. Will I be able to fill through the floor intake while at rest or while at speed or both?

4. If I decide to drain through the floor intake will I have to be at rest to do this or can I drain while at speed as well?

5. Will there be enough pressure from the pump to overcome the water pressure at speed in order to drain?

Thanks for the help!

Bigcatpt